The ILSAC (International Lubricant Standardization and Approval Committee) GF-3 Minimum Performance Standard for Passenger Car Engine Oils, published Oct. 12, 2000 is a cooperative standard from major automobile manufacturers throughout the world and the Engine Manufacturers Association, Inc. This standard specifies the minimum performance requirements (both engine sequence and bench tests) and chemical and physical properties for those engine oils that manufacturers deem necessary for satisfactory equipment performance and life.
Problems with the current situation for the synthesis of lubricant additives outlined above is that they have a high halogen content which is causing increased environmental concerns for the continued use of the lubricants and fuels containing them. Low chlorine or chlorine free lubricants are becoming more and more desirable.
A heretofore preferred manner of making lubricant additives has been to alkylate α-β unsaturated acids or anhydrides in the presence of chlorine then to convert the resulting acylating agent to a derivative such as an ester, amide, imide, or metal salt. This type of reaction yields halogen containing polyalkenyl or hydrocarbyl-substituted acids or anhydrides which may be called alkyl substituted carboxylic acylating agents. The substituted carboxylic acylating agents containing halogen can then be further reacted with amines, polyamines, alcohols, amino-alcohols or metal salts to form halogen containing dispersants, esters and metal salts. It is not uncommon for the polyalkenyl-substituted carboxylic acylating agents to have chlorine contents of 0.5-1%. This corresponds to 5,000-10,000 parts per million chlorine.
Examples of U.S. patents which describe methods for preparing hydrocarbyl-substituted aliphatic carboxylic acylating agents, and particularly polyalkenyl-substituted carboxylic acylating agents utilizing various amounts of chlorine include U.S. Pat. No. 3,215,707 (Rense); U.S. Pat. No. 3,231,587 (Rense); U.S. Pat. No. 3,454,607 (LeSuer); U.S. Pat. Nos. 3,912,764; 4,110,349; 4,234,435 (Meinhardt); and U.S. Pat. No. 5,041,622 (LeSuer). U.S. Pat. No. 4,234,435 describes carboxylic derivative compositions produced by reacting at least one substituted succinic acylating agent with a reactant such as amines, alcohols, reactive metals or combinations thereof. The substituted succinic acylating agent consists of polyalkenyl substituent groups and succinic groups. The substituent groups are derived from a polyalkene having an Mn value of about 1300 to about 5000 and an Mw/ Mn value of about 1.5 to about 4. The acylating agents are characterized by the presence within their structure of an average of more than one succinic group for each equivalent weight of substituent groups. Because of the presence of the excess of succinic groups in the acylating agents, such compounds have been referred to in the art as “over succinated,” and the products described in the '435 patent have also been characterized as detergents and viscosity improving additives in lubricating oil compositions. When such derivatives are incorporated into lubricating compositions, they impart sufficient fluidity modifying properties to the lubricant which are sufficient to permit elimination of all or a significant amount of viscosity index improver from multi-grade lubricant compositions.
The acylating agents utilized in preparing the lubricant additives described in U.S. Pat. No. 4,234,435 are prepared by reaction of polyisobutene polymer with an α-β unsaturated dicarboxylic acid or anhydride such as maleic anhydride in the presence of chlorine. In such instances, the products which are obtained from the reaction and the products obtained from subsequent reaction with amines, alcohols, alcohols and metal compounds contain various amounts of halogen. Due to environmental concerns, it has now become desirable to eliminate or reduce the level of chlorine. One potential solution to eliminating the chlorine contained in such lubricant and fuel additives is simply to not use chlorine in the manufacturing process. Another potential solution is to develop procedures for treating such compositions to remove the chlorine which is present.
One procedure for treating various chlorine-containing organic compounds to reduce the level of chlorine therein has been described in a European patent application published under Publication No. 684 262. The procedure comprises heating, particularly under a nitrogen purge, chlorine containing succinic compounds. U.S. Pat. No. 4,282,157 discusses a method for preparing lower chlorine containing polyalkenyl substituted succinic anhydrides and U.S. Pat. No. 4,330,471 relates to alkylene polyamine derivatives of these succinic anhydrides.
Published European patent application No. 655,242 describes a procedure for reducing the chlorine content of organochlorine compounds comprising introducing a source of iodine or bromine into the organochlorine compound and contacting the components of the resulting mixture for a sufficient amount of time to reduce the chlorine content without substantially incorporating iodine or bromine into the organochlorine compound. This procedure is successful in reducing the chlorine content of organochlorine compounds, but in some instances, it is desirable to even further reduce the amount of chlorine in additive compositions which are to be utilized in lubricants and fuels.
Another published method of reducing the chlorine content of organo-chlorine compounds is described in U.S. Pat. No. 5,489,390. The method comprises treating the chlorine-containing compound with an acid.
As mentioned above, one technique for reducing the amount of chlorine in additive compositions based on polyalkenyl-substituted dicarboxylic acids is to prepare such hydrocarbon-substituted dicarboxylic acids in the absence of chlorine, and procedures have been described for preparing such compounds by the “thermal” process in which the polyolefin and the unsaturated dicarboxylic acid are heated together, optionally in the presence of a catalyst.
U.S. Pat. No. 6,077,909 relates to a method for producing polyolefin substituted carboxylic acylating agents having less than 1000 ppm chlorine and reaction products, such as dispersants, formed therefrom.
U.S. Pat. No. 6,165,235 describes polyolefin substituted carboxylic acylating agents having chlorine content <2000 ppm and having a degree of succination ranging from 1.1-2, said acylating agents being further reacted with amines and/or alcohols to form dispersants having reduced chlorine content.
U.S. Pat. Nos. 4,904,401; 4,938,881; 4,952,328; 4,957,649 and 4,981,602 relate to lubricating oil compositions, particularly to lubricating oil compositions meeting certain industry specifications.
It has now been found that nitrogen-containing carboxylic dispersants having hydrocarbyl substituent groups having a specified minimum number average molecular weight ( Mn), derived from hydrocarbyl substituted acylating agents having a specified minimum degree of succination, having a specified total base number and derived from certain amine reactants, provide lubricants meeting GF-3 and top-tier European lubricant requirements, offer good economics and allow for formulation of low chlorine containing products.
Requirements for top tier lubricants include improved seals performance as measured by the VW Seals test (PV3344), a fluoroelastomer stability test, piston deposits and ring sticking better than a standard, baseline lubricant using the Volkswagen 1.6L Diesel Intercooler test (Volkswagen VW TDI test), and improved extended drain capability as measured by the Volkswagen T4 test (Test method PV 1449)